Integrated circuit for controlling radio communication

ABSTRACT

Provided is a radio communication device which can prevent interference between SRS and PUCCH when the PUCCH transmission bandwidth fluctuates and suppress degradation of CQI estimation accuracy by the band where no SRS is transmitted. The device includes: an SRS code generation unit ( 201 ) which generates an SRS (Sounding Reference Signal) for measuring uplink line data channel quality; an SRS arrangement unit ( 202 ) which frequency-multiplexes the SRS on the SR transmission band and arranges it; and an SRS arrangement control unit ( 208 ) which controls SRS frequency multiplex so as to be uniform in frequency without modifying the bandwidth of one SRS multiplex unit in accordance with the fluctuation of the reference signal transmission bandwidth according to the SRS arrangement information transmitted from the base station and furthermore controls the transmission interval of the frequency-multiplexed SRS.

TECHNICAL FIELD

The present disclosure relates to a radio communication apparatus and aradio communication method.

BACKGROUND ART

Presently, in Third Generation Partnership Project Radio Access NetworkLong Term Evolution (3GPP RAN LTE), an uplink sounding reference signal(SRS) is studied. Here, “sounding” refers to channel quality estimationand an SRS is mainly subject to time-multiplexing and transmitted in aspecific time slot in order to estimate a CQI (Channel QualityIndicator) of an uplink data channel and estimate timing offset betweena base station and a mobile station.

Further, possible methods of transmitting an SRS include the method oftransmitting an SRS in a specific time slot in wideband and estimating aCQI over wideband at a time, and the method of transmitting a narrowbandSRS in a plurality of time slots with shifting frequency bands(frequency hopping) and estimating a CQI over wideband in several times.

Generally, a UE (User Equipment) located near a cell boundary hassignificant path loss and a limitation of maximum transmission power.Accordingly, if an SRS is transmitted in a wideband, received power fora base station per unit frequency decreases and received SNR (Signal toNoise Ratio) decreases, and, as a result, the accuracy of CQI estimationdeteriorates. Therefore, a UE near a cell boundary adopts a narrowbandSRS transmission method of narrowing limited power to a predeterminedfrequency band and performing transmission. In contrast, a UE near thecenter of a cell has small path loss and received power for a basestation per unit frequency can be kept enough, and therefore adopts awideband SRS transmission method.

Meanwhile, another purpose of transmitting an SRS is to estimate timingoffset between a base station and a mobile station. Accordingly, tosecure the given accuracy of timing estimation Δt, the SRS bandwidth inone transmission unit (one frequency multiplexing unit) needs to beequal to or more than 1/Δt. That is, the bandwidth of an SRS in onetransmission unit needs to fulfill both the accuracy of CQI estimationand the accuracy of timing estimation.

Further, in LTE, a PUCCH (Physical Uplink Control Channel), which is anuplink control channel, is frequency-multiplexed on both ends of thesystem band. Accordingly, an SRS is transmitted in the band subtractingthe PUCCHs from the system bandwidth.

Further, the PUCCH transmission bandwidth (a multiple of the number ofchannels of one PUCCH bandwidth) varies according to the number of itemsof control data to be accommodated. That is, when the number of items ofcontrol data to be accommodated is small, the PUCCH transmissionbandwidth becomes narrow (the number of channels becomes few) and,meanwhile, when the number of items of control data to be accommodatedis great, the PUCCH transmission bandwidth becomes wide (the number ofchannels becomes large). Therefore, as shown in FIG. 1, when the PUCCHtransmission bandwidth varies, the SRS transmission bandwidth alsovaries. In FIG. 1, the horizontal axis shows frequency domain, and thevertical axis shows time domain (same as below). In the following, thebandwidth of one channel of a PUCCH is simply referred to as the “PUCCHbandwidth” and the bandwidth by multiplying the PUCCH bandwidth by thenumber of channels is referred to as the “PUCCH transmission bandwidth.”Likewise, the bandwidth of an SRS in one transmission unit is simplyreferred to as the “SRS bandwidth” and the bandwidth of an SRS in aplurality of transmission units is referred to as “SRS transmissionbandwidth.”

Non-Patent Document 1: 3GPP R1-072229, Samsung, “Uplink channel soundingRS structure,” 7th-11th May 2007

BRIEF SUMMARY

In Non-Patent Document 1, the method shown in FIG. 2 is disclosed as anarrowband SRS transmission method in a case where a PUCCH transmissionbandwidth varies. In the SRS transmission method disclosed in Non-PatentDocument 1, as shown in FIG. 2, the SRS transmission bandwidth is fixedto the SRS transmission bandwidth of when the PUCCH transmissionbandwidth is the maximum and is not changed even when the PUCCHtransmission bandwidth varies. Further, as shown in FIG. 2, when an SRSis transmitted in a narrowband, the SRS is frequency-hopped andtransmitted. According to the method described in Non-Patent Document 1,when the PUCCH transmission bandwidth is less than the maximum valueshown in the bottom part of FIG. 2, bands in which SRSs are nottransmitted are produced, and the accuracy of CQI estimationsignificantly deteriorates in the frequency domain.

Further, as shown in FIG. 3A, if the SRS transmission bandwidth is fixedto the SRS transmission bandwidth of when the PUCCH transmissionbandwidth is the minimum, SRSs and PUCCHs interfere with each other whenthe PUCCH transmission bandwidth increases as shown in FIG. 3B, thePUCCH reception performance deteriorates.

To prevent SRSs and PUCCHs from interfering with each other as shown inFIG. 3B when the PUCCH transmission bandwidth increases, the method ofstopping transmission of an SRS interfering with a PUCCH as shown inFIG. 4B is possible. Here, FIG. 4A is the same as FIG. 3A and shown toclarify the explanation in an overlapping manner. According to thismethod, bands in which SRSs are not transmitted are produced, and theaccuracy of CQI estimation deteriorates in the frequency domain.

An embodiment provides a radio communication apparatus and a radiocommunication method that facilitate reducing the deterioration of theaccuracy of CQI estimation due to bands in which SRSs are nottransmitted while preventing interference between SRSs and PUCCHs, incases where the PUCCH transmission bandwidth varies in narrowband SRStransmission.

The radio communication apparatus of an embodiment adopts aconfiguration including: a generation section that generates a referencesignal for measuring uplink data channel quality; a mapping section thatfrequency-multiplexes and maps the reference signal to a referencesignal transmission band in which the reference signal is transmitted;and a control section that controls positions in which thefrequency-multiplexing is performed such that the positions in which thefrequency multiplexing is performed are placed evenly in a frequencydomain without changing the bandwidth of one multiplexing unit of thereference signals according to a variation of a transmission bandwidthof the reference signals.

The radio communication method according to an embodiment includes stepsof: generating a reference signal for estimating uplink data channelquality; frequency-multiplexing and mapping the reference signal to areference signal transmission band in which the reference signal istransmitted; and controlling positions in which thefrequency-multiplexing is performed such that the positions in which thefrequency-multiplexing is performed are placed evenly in a frequencydomain without changing the bandwidth of one multiplexing unit of thereference signals according to a variation of a transmission bandwidthof the reference signals.

According to an embodiment, it is possible to reduce the deteriorationof the accuracy of CQI estimation due to bands in which SRSs are nottransmitted while preventing interference between SRSs and PUCCHs incases where the PUCCH transmission bandwidth varies in narrowband SRStransmission.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a conventional case of how the SRS transmission bandwidthvaries according to the variations of the PUCCH transmission bandwidth;

FIG. 2 shows a conventional narrowband SRS transmission method used whenthe PUCCH transmission bandwidth varies;

FIG. 3A shows an example of a conventional narrowband SRS transmissionmethod used when the PUCCH transmission bandwidth varies;

FIG. 3B shows an example of a conventional narrowband SRS transmissionmethod used when the PUCCH transmission bandwidth varies;

FIG. 4A shows an example of a conventional narrowband SRS transmissionmethod used when the PUCCH transmission bandwidth varies;

FIG. 4B shows an example of a conventional narrowband SRS transmissionmethod used when the PUCCH transmission bandwidth varies;

FIG. 5 is a block diagram showing the configuration of the base stationaccording to Embodiment 1;

FIG. 6 is a block diagram showing the configuration of the mobilestation according to Embodiment 1;

FIG. 7 is a flow chart showing the processing steps in the SRSallocation determination section according to Embodiment 1;

FIG. 8A shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 1;

FIG. 8B shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 1;

FIG. 9 is a flow chart showing the processing steps in the SRSallocation determination section according to Embodiment 2;

FIG. 10A shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 2;

FIG. 10B shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 2;

FIG. 11A shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 3;

FIG. 11B shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 3;

FIG. 12A shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 4;

FIG. 12B shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 4;

FIG. 13A shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 5;

FIG. 13B shows an allocation example of SRSs determined in the SRSallocation determination section according to Embodiment 5;

FIG. 14A shows an allocation example (example 1) of SRSs determined inan example of the SRS allocation determination section according to anembodiment;

FIG. 14B shows an allocation example (example 1) of SRSs determined inan example of the SRS allocation determination section according to anembodiment;

FIG. 15A shows an allocation example (example 2) of SRSs determined inan example of the SRS allocation determination section according to anembodiment;

FIG. 15B shows an allocation example (example 2) of SRSs determined inan example of the SRS allocation determination section according to anembodiment;

FIG. 16 shows an example of the SRS allocation definition tableaccording to the present embodiment;

FIG. 17A shows an allocation example (example 3) of SRSs determined inan example of the SRS allocation determination section according to anembodiment;

FIG. 17B shows an allocation example (example 3) of SRSs determined inan example of the SRS allocation determination section according to anembodiment;

FIG. 18A shows an allocation example (example 4) of SRSs determined inan example of the SRS allocation determination section according to anembodiment; and

FIG. 18B shows an allocation example (example 4) of SRSs determined inan example of the SRS allocation determination section according to anembodiment.

DETAILED DESCRIPTION

Now, example embodiments will be described in detail with reference tothe accompanying drawings.

Embodiment 1

FIG. 5 shows the configuration of base station 100 according toEmbodiment 1, and FIG. 6 shows the configuration of mobile station 200according to Embodiment 1.

To avoid complicated explanation, FIG. 5 shows components involving SRSreception closely relating to the present disclosure, and drawings andexplanations of the components involving uplink and downlink datatransmission and reception are omitted. Likewise, FIG. 6 showscomponents involving SRS transmission closely relating to the presentdisclosure and, drawings and explanations of the components involvinguplink and downlink data transmission and reception are omitted.

In base station 100 shown in FIG. 5, SRS allocation determinationsection 101 determines allocation of SRSs in the frequency domain andthe time domain based on the number of PUCCH channels, and outputsinformation related to the determined SRS allocation (hereinafter “SRSallocation information”), to control signal generation section 102 andSRS extraction section 108. The processing in SRS allocationdetermination section 101 will be described later in detail. Controlsignal generation section 102 generates a control signal including SRSallocation information, and outputs the generated control signal tomodulation section 103. Modulation section 103 modulates the controlsignal, and outputs the modulated control signal to radio transmittingsection 104. Radio transmitting section 104 performs transmittingprocessing including D/A conversion, up-conversion and amplification, onthe modulated signal, and transmits the resulting signal from antenna105.

Radio receiving section 106 receives SRSs via radio from mobile station200 via antenna 105, performs receiving processing includingdown-conversion and A/D conversion on the SRSs and outputs the SRSsafter receiving processing to demodulation section 107. Demodulationsection 107 demodulates the received SRSs and outputs the demodulatedSRSs to SRS extraction section 108. SRS extraction section 108 extractsSRSs allocated in the frequency domain and the time domain based on theSRS allocation information received as input from SRS allocationdetermination section 101, and outputs the extracted SRSs to CQI/timingoffset estimation section 109. CQI/timing offset estimation section 109estimates CQIs and timing offset from the SRSs.

In mobile station 200 shown in FIG. 6, SRS code generation section 201generates a code sequence used as an SRS for measuring uplink datachannel quality, that is, generates an SRS code, and outputs the SRScode to SRS allocation section 202. SRS allocation section 202 maps theSRS code to resources in the time domain and frequency domain accordingto SRS allocation control section 208, and outputs the mapped SRS codeto modulation section 203. Modulation section 203 modulates the SRS codeand outputs the modulated SRS code to radio transmitting section 204.Radio transmitting section 204 performs transmitting processingincluding D/A conversion, up-conversion and amplification, on themodulated signal, and transmits the resulting signal from antenna 205.

Radio receiving section 206 receives a control signal via radio frombase station 100 via antenna 205, performs receiving processingincluding down-conversion and A/D conversion on the control signal andoutputs the control signal after receiving processing to demodulationsection 207. Demodulation section 207 demodulates the received controlsignal and outputs the demodulated control signal to SRS allocationcontrol section 208. SRS allocation control signal 208 controls SRSallocation section 202 according to the SRS allocation informationincluded in the demodulated control signal.

Next, the processing in SRS allocation determination section 101 in basestation 100 will be explained in detail.

FIG. 7 is a flow chart showing the processing steps in SRS allocationdetermination section 101.

First, in step (hereinafter “ST”) 1010, SRS allocation determinationsection 101 determines an SRS bandwidth based on the accuracy of CQIestimation and the accuracy of timing offset estimation.

Next, in ST 1020, SRS allocation determination section 101 calculatesthe number of SRSs to be multiplexed in the frequency domain based onthe system bandwidth, the number of PUCCH channels and the SRSbandwidth. To be more specific, the number of SRSs to be multiplexed inthe frequency domain is the maximum number of SRSs which can bemultiplexed on the SRS transmission bandwidth obtained by subtractingthe PUCCH transmission bandwidth from the system bandwidth, and whicheach have a bandwidth of one transmission unit determined in ST 1010.That is, the number of SRSs to be multiplexed in the frequency domain isthe integer part of the quotient obtained by dividing the SRStransmission bandwidth by the SRS bandwidth determined in ST 1010. Here,the PUCCH transmission bandwidth is determined by the number of PUCCHchannels, and varies according to the number of items of control data tobe accommodated.

Next, in ST 1030, SRS allocation determination section 101 firstdetermines allocation of SRSs such that the SRSs are frequency-hopped(frequency-multiplexed) in the SRS transmission bandwidth atpredetermined time intervals. To be more specific, SRS allocationdetermination section 101 determines that SRSs are mapped in thefrequency domain and time domain such that the SRSs cover the frequencyband to be subject to CQI estimation evenly and are mapped atpredetermined time intervals in the time domain.

FIGS. 8A and 8B show examples of SRS allocation determined in SRSallocation determination section 101. FIG. 8A shows a case where thenumber of PUCCH channels is two, and FIG. 8B shows a case where thenumber of PUCCH channels is four.

In FIGS. 8A and 8B, the SRS bandwidths are determined so as to fulfillthe required accuracy of CQI estimation and the required accuracy oftiming offset, and are not changed even when the number of PUCCHchannels and SRS transmission bandwidth vary.

Further, the number of PUCCH channels varies between FIGS. 8A and 8B,and therefore, the SRS transmission bandwidth varies and the number ofSRSs to be frequency-multiplexed, that is, the number of SRS hopping,obtained by dividing the SRS transmission bandwidth by the SRSbandwidths determined in ST 1010, varies. When the number of PUCCHchannels is two in FIG. 8A, the number of SRSs to befrequency-multiplexed is four, and, when the number of PUCCH channels isfour in FIG. 8B, the number of SRSs to be frequency-multiplexed isthree.

Then, as shown in FIG. 8, the positions where SRSs arefrequency-multiplexed in the SRS transmission bandwidth are positions tocover the SRS transmission band evenly, that is, the frequency bandsubject to CQI estimation. This results in dividing the band in whichSRSs are not transmitted into a number of bands having smallerbandwidths, that is, this prevents SRSs from being not transmitted overa specific wide range of a band, so that it is possible to reduce thedeterioration of the accuracy of CQI estimation due to bands in whichSRSs are not transmitted.

In this way, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRS allocation ischanged to cover a CQI estimation bandwidth with fixed SRS bandwidthsevenly, so that, when the PUCCH transmission bandwidth varies, it ispossible to prevent interference between SRSs and PUCCHs whilemaintaining the accuracy of CQI estimation and the accuracy of timingoffset estimation, and reduce the deterioration of the accuracy of CQIestimation due to bands in which SRSs are not transmitted.

Embodiment 2

The base station and the mobile station according to Embodiment 2 adoptthe same configurations and basically perform the same operations as thebase station and the mobile station according to Embodiment 1.Therefore, block diagrams are not shown here, and the description willbe omitted in detail. The base station and the mobile station accordingto the present embodiment are different from the base station and themobile station according to Embodiment 1 in the SRS allocationdetermination section in the base station. The SRS allocationdetermination section provided in the base station according to thepresent embodiment is different from SRS allocation determinationsection 101 provided in the base station according to Embodiment 1 inpart of processing.

Now, the processing in the SRS allocation determination sectionaccording to the present embodiment will be explained.

FIG. 9 is a flow chart showing the processing steps in the SRSallocation determination section according to the present embodiment.The steps shown in FIG. 9 are basically the same as shown in FIG. 7 andthe same reference numerals are assigned to the same steps, andtherefore the explanation thereof will be omitted. The steps shown inFIG. 9 are different from the steps shown in FIG. 7 in having ST 2030instead of ST 1030.

In ST 2030, the SRS allocation determination section first calculatesthe time interval at which SRSs are mapped in the frequency domain andtime domain according to the following equation 1. If the SRSs aretransmitted using time interval τ(c_(PUCCH)) calculated according toequation 1, the CQI estimation period in the CQI estimation target bandis fixed even if the number of PUCCH channels varies.

[1]

τ(c _(PUCCH))=T/n(c _(PUCCH))   (Equation 1)

In equation 1, T represents the CQI estimation period in the CQIestimation target band and c_(PUCCH) represents the number of PUCCHchannels. n(c_(PUCCH)) represents the number of SRSs to befrequency-multiplexed, that is, the number of frequency hopping, whenthe number of PUCCH channels is c_(PUCCH). The transmission interval isbased on a time slot unit, and therefore τ(c_(PUCCH)) is a result of thevalue on the right hand side of equation 1 matched with a time slot.

Further, in ST 2030, the SRS allocation determination section determinesallocation of SRSs such that SRSs are frequency-multiplexed in the SRStransmission bandwidth at the calculated time interval τ. To be morespecific, SRS allocation determination section determines to map SRSs soas to cover the frequency band subject to CQI estimation target evenlyin the frequency domain and to cover CQI estimation period T evenly inthe time domain.

FIGS. 10A and 10B show examples of SRS allocation determined in the SRSallocation determination section according to the present embodiment.FIG. 10 is basically the same as FIG. 8 and the overlapping explanationwill be omitted.

In FIGS. 10A and 10B, the SRS bands are not changed in accordance with avariation of SRS transmission bandwidth, and SRSs arefrequency-multiplexed so as to cover the SRS transmission bandwidthevenly.

Further, in FIG. 10A, SRSs are mapped using time interval τ(2), and inFIG. 10B, SRSs are mapped using time interval τ(4). That is, in thepresent embodiment, when the number of PUCCH channels decreases, the SRStransmission interval is made shorter and when the number of PUCCHchannels increases, the SRS transmission interval is made longer. Bythis means, even when the number of PUCCH channels varies, CQIestimation period T does not vary.

In this way, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRS allocation ischanged such that a CQI estimation bandwidth is covered with fixing SRSbandwidths evenly. Accordingly, when the PUCCH transmission bandwidthvaries, it is possible to prevent SRSs and PUCCHs from interfering eachother while maintaining the accuracy of CQI estimation and the accuracyof timing offset, and reduce the deterioration of the accuracy of CQIestimation due to bands in which SRSs are not transmitted.

Further, according to the present embodiment, when the number of PUCCHchannels decreases, the SRS transmission interval is made shorter andwhen the number of PUCCH channels increases, the SRS transmissioninterval is made longer. By this means, when the PUCCH transmissionbandwidth varies, it is possible to maintain a constant CQI estimationperiod and prevent the accuracy of CQI estimation from deteriorating.

Embodiment 3

The base station and the mobile station according to Embodiment 3 adoptthe same configurations and basically perform the same operations as thebase station and the mobile station according to Embodiment 1.Therefore, block diagrams are not shown here, and the description willbe omitted in detail. The base station and the mobile station accordingto the present embodiment are different from the base station and themobile station according to Embodiment 1 in the SRS allocationdetermination section in the base station. The SRS allocationdetermination section provided in the base station according to thepresent embodiment is different from SRS allocation determinationsection 101 provided in the base station according to Embodiment 1 inpart of processing.

Now, the allocation of SRSs determined in the SRS allocationdetermination section according to the present embodiment will beexplained.

FIGS. 11A and 11B show examples of SRS allocation determined in the SRSallocation determination section according to the present embodiment.FIG. 11 is basically the same as FIG. 10 and the overlapping explanationwill be omitted.

In FIGS. 11A and 11B, the SRS bands are not changed in accordance with avariation of SRS transmission bandwidth, and SRSs arefrequency-multiplexed so as to cover the SRS transmission bandwidthevenly.

Further, as shown in FIGS. 11A and 11B, the number of SRSs to befrequency-multiplexed is the number of when the number of PUCCH channelsis the maximum, regardless of whether the number of PUCCHs increases ordecreases. Here, the maximum value for the number of PUCCH channels isfour and the number of SRSs to be frequency-multiplexed is three.

Further, as shown in FIGS. 11A and 11B, a transmission interval betweenSRSs is the transmission interval of when the number of PUCCH channelsis the maximum, regardless of whether the number of PUCCHs increases ordecreases. Here, the maximum value for the number of PUCCH channels isfour and the transmission interval is represented by τ(4). According tothe method as shown in FIG. 11, it is not necessary to calculate atransmission interval every time the number of PUCCH channels varies andit is possible to simplify the determination processing of SRSallocation.

In this way, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRS allocation ischanged such that a CQI estimation bandwidth is evenly covered withfixing SRS bandwidths. By this means, when the PUCCH transmissionbandwidth varies, it is possible to prevent SRSs and PUCCHs frominterfering each other while maintaining the accuracy of CQI estimationand the accuracy of timing offset, and reduce the deterioration of theaccuracy of CQI estimation due to bands in which SRSs are nottransmitted.

Furthermore, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRSs are mappedwithout changing the number of SRSs to be frequency-multiplexed and theSRS transmission interval, so that it is possible to simplify the SRSallocation process.

Embodiment 4

In Embodiment 4, the method of SRS allocation from a plurality of mobilestations in accordance with a variation of the PUCCH transmissionbandwidth, will be explained.

The base station and the mobile station according to Embodiment 4 adoptthe same configurations and basically perform the same operations as thebase station and the mobile station according to Embodiment 1.Therefore, block diagrams are not shown here, and the description willbe omitted in detail. The base station and the mobile station accordingto the present embodiment are different from the base station and themobile station according to Embodiment 1 in the SRS allocationdetermination section in the base station. The SRS allocationdetermination section provided in the base station according to thepresent embodiment is different from SRS allocation determinationsection 101 provided in the base station according to Embodiment 1 inpart of processing.

Now, the allocation of SRSs determined in the SRS allocationdetermination section according to the present embodiment will beexplained.

FIGS. 12A and 12B show examples of SRS allocation determined in the SRSallocation determination section according to the present embodiment.FIG. 12 is basically the same as FIG. 8 and the overlapping explanationwill be omitted.

In FIGS. 12A and 12B, the SRS bands are not changed in accordance with avariation of SRS transmission bandwidth, and SRSs arefrequency-multiplexed so as to cover the SRS transmission bandwidthevenly.

Further, as shown in FIGS. 12A and 12B, in accordance with the variationof the PUCCH transmission bandwidth, the SRS allocation determinationsection according to the present embodiment maps SRSs without changingthe hopping pattern of SRSs in a predetermined frequency band. In otherwords, SRS allocation to be changed is controlled so as to makedifferent hopping patterns in the same band. To be more specific, bytransmitting and not transmitting SRSs mapped to the specific bandaccording to an increase and decrease of the PUCCH transmissionbandwidth, it is not necessary to change the hopping pattern in otherbands.

In this way, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRS allocation ischanged such that a CQI estimation bandwidth is evenly covered withfixing SRS bandwidths. By this means, when the PUCCH transmissionbandwidth varies, it is possible to prevent SRSs and PUCCHs frominterfering each other while maintaining the accuracy of CQI estimationand the accuracy of timing offset, and reduce the decrease of theaccuracy of CQI estimation due to bands in which SRSs are nottransmitted.

Further, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRSs are mappedin the frequency domain and time domain without changing the SRS hoppingpattern, so that, when the PUCCH transmission bandwidth varies, it ispossible to maintain the number of SRSs from mobile stations to bemultiplexed and the CQI estimation period in the CQI estimation targetband of each mobile station.

Embodiment 5

The base station and the mobile station according to Embodiment 5 adoptthe same configurations and basically perform the same operations as thebase station and the mobile station according to Embodiment 1.Therefore, block diagrams are not shown here, and the description willbe omitted in detail. The base station and the mobile station accordingto the present embodiment are different from the base station and themobile station according to Embodiment 1 in the SRS allocationdetermination section in the base station. The SRS allocationdetermination section provided in the base station according to thepresent embodiment is different from SRS allocation determinationsection 101 provided in the base station according to Embodiment 1 inpart of processing.

Now, the allocation of SRSs determined in the SRS allocationdetermination section according to the present embodiment will beexplained.

FIGS. 13A and 13B show examples of SRS allocation determined in the SRSallocation determination section according to the present embodiment.

In FIGS. 13A and 13B, the SRS bands are not changed in accordance with avariation of SRS transmission bandwidth, and SRSs arefrequency-multiplexed so as to cover the SRS transmission bandwidthevenly.

Further, in FIGS. 13A and 13B, the number of SRSs to befrequency-multiplexed is the number of when the number of PUCCH channelsis the minimum and is fixed regardless of whether the number of PUCCHsincreases or decreases. In FIGS. 13A and 13B, the minimum value for thenumber of PUCCH channels is two and the number of SRSs to befrequency-multiplexed is four.

Further, in FIGS. 13A and 13B, while the SRS transmission bandwidthvaries in accordance with an increase and decrease of the number ofPUCCH channels, the number of SRSs to be frequency-multiplexed is fixed,and therefore SRSs are mapped in the frequency domain such that aplurality of SRSs partly overlap.

Further, in FIGS. 13A and 13B, the number of SRSs to befrequency-multiplexed does not change in accordance with an increase anddecrease of the number of PUCCH channels, and therefore SRS transmissionintervals do not change.

In this way, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRS allocation ischanged such that a CQI estimation bandwidth is covered with fixing SRSbandwidths evenly. Accordingly, when the PUCCH transmission bandwidthvaries, it is possible to prevent interference between an SRS and aPUCCH while maintaining the accuracy of CQI estimation and the accuracyof timing offset, and reduce the deterioration of the accuracy of CQIestimation due to bands in which SRSs are not transmitted.

Further, according to the present embodiment, in accordance with anincrease and decrease of the number of PUCCH channels, SRS are mappedsuch that bands of frequency-multiplexed SRSs partly overlap, withoutchanging the number of SRSs to be frequency-multiplexed, so that it ispossible to improve the accuracy of CQI estimation more and prevent theaccuracy of CQI estimation from deteriorating due to bands in which SRSsare not transmitted.

The example embodiments have been explained.

Although cases have been explained with the above embodiments where thenumber of PUCCH channels is two or four, the number is explained withexamples only and the present disclosure is not limited to this.

Further, although cases have been explained with the above embodimentswhere the SRS transmission bandwidth is the band obtained by subtractingthe PUCCH transmission bandwidth from the system bandwidth, the presentdisclosure is not limited to this, and the SRS transmission bandwidthmay be a specific band varying according to an increase and decrease ofthe number of PUCCH channels.

Further, although cases have been explained with the above embodimentsas examples where the SRS bands are not changed in accordance with anincrease and decrease of the number of PUCCH channels and the positionson which SRSs are frequency-multiplexed in the SRS transmission bandchange, the present disclosure is not limited to this, and it ispossible to change the positions where SRSs are frequency-multiplexed inthe SRS transmission band according to an increase and decrease of thenumber of PUCCH channels, and change the SRS bandwidths. A variation ofan SRS bandwidth may be limited within a range in which thedeterioration of the accuracy of CQI estimation and the accuracy oftiming offset can be ignored, for example within ±1 to 2 RBs, and thisfacilitates reducing the deterioration of the accuracy of CQIestimation. Here, an RB (Resource Block) refers to a unit representing aspecific range of radio resources. FIG. 14A shows an example where theSRS bands extend in a predetermined range and the range of each extendedband in FIG. 14A is 1 RB or less. Further, to extend and contract theSRS transmission band here, CAZAC (Constant Amplitude ZeroAuto-Correlation) sequence or cyclic extension and truncation of asequence having the same characteristics as CAZAC may be adopted.

Further, it is possible to allocate uplink data channels for which CQIscannot be estimated using narrowband SRSs with the above embodiments, tomobile stations transmitting wideband SRSs with priority. FIG. 14Billustrates to explain a case where uplink data channels for which CQIscannot be estimated using narrowband SRSs are allocated with priority tomobile stations transmitting wideband SRSs. The above packet allocationmethod makes it possible to prevent the frequency scheduling effect fromlowering.

Further, as shown in FIG. 15A, SRSs may be mapped so as to neighborPUCCHs. Further, as shown in FIG. 15B, allocation of SRSs may varybetween hopping cycles.

Further, an SRS may be named as simply a “pilot signal,” “referencesignal” and so on.

Further, a known signal used for an SRS may include a CAZAC sequence ora sequence having the same characteristics as a CAZAC.

Further, the SRS allocation information acquired in the base stationaccording to the above embodiments may be reported to mobile stationsusing a PDCCH (Physical Downlink Control Channel), which is an L1/L2control channel, or using a PDSCH (Physical Downlink Shared Channel) asan L3 message.

Further, in the above embodiments, DFT-s-OFDM (Discrete FourierTransform-spread-Orthogonal Frequency Division Multiplexing) employed inLTE may be adopted to the uplink.

Further, in the above embodiments, OFDM employed in LTE may be adoptedto downlink.

Further, the SRS allocation information according to the aboveembodiments may be uniquely associated in advance with a broadcastchannel, for example, PUCCH configuration information reported in a BCH(Broadcast Channel). By this means, it is not necessary to transmit SRSallocation information on a per UE basis, so that signaling overhead isreduced. For example, each UE may calculate SRS allocation from thenumber of PUCCH channels as follows.

Now, an example of equations to calculate SRS allocation from the numberof PUCCH channels will be shown below.

If the subcarrier to which an SRS starts to be mapped in the frequencydomain is k₀, k₀ is represented as the following equation 2.

[2]

k ₀ =k _(RB)(n)·N _(SC) ^(RB)   (Equation 2)

In equation 2, n represents the multiplexing number of an SRS in thefrequency domain and N_(sc) ^(RB) represents the number of subcarriersper RB. Further, k_(RB)(n) represents the RB number to which the SRSwith frequency multiplex number n is mapped and is represented by thefollowing equation 3 or 4.

$\begin{matrix}{\mspace{20mu} \lbrack 3\rbrack} & \; \\{{{k_{RB}(n)} = {N_{SRS}^{BASE} + \left\lfloor {\left( {n + 1} \right) \cdot \frac{N_{RB}^{UL} - N_{RB}^{PUCCH} - {N_{SRS}^{BASE} \cdot N_{SRS}}}{N_{SRS} + 1}} \right\rfloor + \left\lfloor \frac{N_{RB}^{PUCCH}}{2} \right\rfloor}}\mspace{20mu} {{n = 0},1,{{\ldots \mspace{14mu} N_{SRS}} - 1}}} & \left( {{Equation}\mspace{14mu} 3} \right) \\{\mspace{20mu} \lbrack 4\rbrack} & \; \\{{{k_{RB}(n)} = {{n \cdot N_{SRS}^{BASE}} + \left\lfloor {\left( {{2n} + 1} \right) \cdot \frac{N_{RB}^{UL} - N_{RB}^{PUCCH} - {N_{SRS}^{BASE} \cdot N_{SRS}}}{2N_{SRS}}} \right\rfloor + \left\lfloor \frac{N_{RB}^{PUCCH}}{2} \right\rfloor}}\mspace{20mu} {{n = 0},1,{{\ldots \mspace{14mu} N_{SRS}} - 1}}} & \left( {{Equation}\mspace{14mu} 4} \right)\end{matrix}$

In equations 3 and 4, N_(SRS) represents the number of SRSs to befrequency-multiplexed and is represented by the following equation 5.

$\begin{matrix}\lbrack 5\rbrack & \; \\{N_{SRS} = \left\lfloor \frac{N_{RB}^{UL} - N_{RB}^{PUCCH}}{N_{SRS}^{BASE}} \right\rfloor} & \left( {{Equation}\mspace{14mu} 5} \right)\end{matrix}$

In equations 3, 4 and 5, N_(RB) ^(PUCCH) represents the number of RBsincluded in the PUCCH transmission band and N_(RB) ^(UL) represents thenumber of RBs included in the system band. N_(SRS) ^(BASE) representsthe number of RBs included in the SRS transmission bandwidth.

In the above parameters, the parameters other than N_(RB) ^(PUCCH) aresystem parameters, so that the system parameters can be used in a fixedmanner once they are signaled or reported. Accordingly, when a mobilestation is given N_(RB) ^(PUCCH), SRS allocation is able to be derivedaccording to the above equation 2 to equation 5. Here, N_(RB) ^(PUCCH)the parameter determined by the number of PUCCH channels, so that amobile station is able to derive SRS allocation and transmit SRSs if themobile station is provided the number of PUCCH channels from the basestation.

Further, the mobile station may derive SRS allocation from the number ofPUCCH channels with reference to an SRS allocation definition tableinstead of above equation 2 to equation 5. FIG. 16 shows an example ofthe SRS allocation definition table. The SRS allocation definition tableshown in FIG. 16 defines the RB numbers of RBs to which SRSs are mappedin cases where the number of PUCCH channels is one and four. Further, trepresents a transmission timing in hopping cycles. Further, as shown inFIG. 16, the hopping patterns vary according to varying multiplexingnumber of SRSs to n. Further, “−” in the table shows that SRSs are notallocated. By holding an SRS allocation definition table, a mobilestation is able to derive SRS allocation and transmit SRSs if the mobilestation is provided the number of PUCCH channels from the base station.

Further, the information uniquely associated in advance with PUCCHconfiguration information may include other SRS configurationinformation including variable information about the above SRS bandwidthand SRS sequence information, in addition to the SRS allocationinformation.

Further, although examples have been explained with the aboveembodiments where the narrowband SRS bandwidths evenly cover one SRStransmission bandwidth in the frequency domain, the present disclosureis not limited to this, and, with the present disclosure, one SRStransmission bandwidth may be divided into a plurality of smaller SRStransmission bandwidths (hereinafter “SRS subbands”) and the narrowbandSRS bandwidths may be mapped so as to cover each SRS subband bandwidthevenly in the frequency domain.

FIGS. 17A and 17B show an example of a case where two SRS subbands 1 and2 are provided in one SRS transmission bandwidth and three SRSs aremapped to each subband.

In the example shown in FIG. 17A, the allocation and the intervals ofSRSs mapped in SRS subband 1 are changed according to the variation of abandwidth of SRS subband 1 such that CQI estimation bandwidth is coveredevenly in SRS subband 1. Likewise, the allocation and the intervals ofSRSs mapped in SRS subband 2 are changed according to the variation of abandwidth of SRS subband 2 such that CQI estimation bandwidth is coveredevenly in SRS subband 2.

Further, as in the example shown in FIG. 17B, the bandwidths of SRSsubbands may vary. In this case, the allocation and the intervals ofSRSs mapped in SRS subbands may be changed on a per SRS subband basissuch that CQI estimation bandwidth is evenly covered.

Although a case has been explained as an example where the number of SRSsubbands is two in FIGS. 17A and 17B, the number of SRS subbands may bethree or more with the present disclosure. Further, although a case hasbeen explained as an example where the number of SRSs in the SRS subbandis three in FIGS. 17A and 17B, with the present disclosure, a pluralityof SRSs besides three SRSs may be mapped in the SRS subband.

Further, although mapping examples have been explained with the aboveembodiments where SRSs are neighboring each other evenly in the SRStransmission bandwidth, in practical systems, SRS bandwidths andpositions where SRSs are allocated in the frequency domain are discretevalues. Therefore, cases may occur where the SRS transmission bandwidthis not divided by one SRS band. In this case, without using frequencyallocation units that have fractions left as a remainder of division, itis also possible to map SRSs so as to cover the CQI estimation bandwidthevenly in the frequency domain in a range that is divisible (FIG. 18A).Further, it is also possible to allocate frequency allocation units thathave fractions left as a remainder of division between SRSs on a perfrequency unit basis (FIG. 18B).

Here, the RB (Resource Block) in FIGS. 18A and 18B represents anallocation unit in the frequency domain. FIGS. 18A and 18B are exampleswhere the SRS bandwidth is 4 RBs and the SRS transmission bandwidth is18 RBs.

Further, although cases have been explained with the above embodimentswhere SRSs are frequency-hopped (frequency-multiplexed) in the SRStransmission bandwidth at predetermined time intervals, the presentdisclosure is not limited to this, and provides the same advantage as incases where frequency hopping is not carried out, as explained with theabove embodiments.

The SRSs in the above embodiments may be mapped in RB units orsubcarrier units, and may not be limited to any unit.

Further, a CQI showing channel quality information may be referred to as“CSI (Channel State Information).”

Further, a base station apparatus may be referred to as “Node B” and amobile station may be referred to as “UE.”

Further, although cases have been described with the above embodimentsas examples where the present disclosure is configured by hardware, thepresent disclosure can also be realized by software.

Each function block employed in the description of each of theaforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSIs, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of a programmableFPGA (Field Programmable Gate Array) or a reconfigurable processor whereconnections and settings of circuit cells within an LSI can bereconfigured is also possible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosures of Japanese Patent Application No. 2007-211548, filed onAug. 14, 2007, and Japanese Patent Application No. 2008-025535, filed onFeb. 5, 2008, including the specifications, drawings and abstracts, areincorporated herein by reference in their entirety.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to, for example, mobilecommunication systems.

1. An integrated circuit to control a process, the process comprising: mapping, in at least one mode of operation, a reference signal to each of one or more frequency resources, into which a frequency band having a transmission bandwidth is uniformly divided depending on a size variation of the transmission bandwidth within a system bandwidth, wherein the transmission bandwidth is provided between control channels mapped to both ends of the system bandwidth; and transmitting, in at least the one mode of operation, the reference signal.
 2. The integrated circuit according to claim 1, comprising: circuitry which, in operation, controls the process; at least one input coupled to the circuitry, wherein the at least one input, in operation, inputs data; and at least one output coupled to the circuity, wherein the at least one output, in operation, outputs data.
 3. The integrated circuit according to claim 1 wherein the transmission bandwidth is variable in the system bandwidth while a central frequency of the transmission bandwidth remains the same.
 4. The integrated circuit according to claim 1 wherein in at least one mode of operation, each of the one or more frequency resources has a fixed bandwidth regardless of the variation of the transmission bandwidth.
 5. The integrated circuit according to claim 1 wherein in at least one mode of operation, the one or more frequency resources are uniformly dispersed in the frequency band having the transmission bandwidth.
 6. The integrated circuit according to claim 1, wherein the process comprises receiving, in at least the one mode of operation, control information associated with a reference-signal mapping, and the mapping includes mapping of the reference signal based on the control information.
 7. The integrated circuit according to claim 1 wherein the frequency band having the transmission bandwidth is obtained by subtracting a band, to which the control channels are mapped, from the system bandwidth.
 8. The integrated circuit according to claim 1 wherein in at least one mode of operation, each of the one or more frequency resources has a narrow bandwidth, and the transmission bandwidth is a wide bandwidth.
 9. The integrated circuit according to claim 1 wherein in at least one mode of operation, the one or more frequency resources consists of a single frequency resource having the transmission bandwidth.
 10. The integrated circuit according to claim 1 wherein in at least one mode of operation, the one or more frequency resources comprises a plurality of frequency resources and the mapping includes mapping of the reference signal with frequency hopping using each of the plurality of frequency resources.
 11. The integrated circuit according to claim 1 wherein in at least one mode of operation, the one or more frequency resources consists of a single frequency resource having the transmission bandwidth and the mapping includes mapping of the reference signal without frequency hopping.
 12. The integrated circuit according to claim 1 wherein the transmission bandwidth is one of a plurality of different transmission bandwidths.
 13. The integrated circuit according to claim 1 wherein each of the one or more frequency resources is a unit of transmission of a reference signal.
 14. The integrated circuit according to claim 1 wherein a number of the one or more frequency resources is different depending on the variation of the transmission bandwidth.
 15. The integrated circuit according to claim 1 wherein the one or more frequency resources cover the frequency band of the transmission bandwidth.
 16. The integrated circuit according to claim 1 wherein in at least one mode of operation, the one or more frequency resources comprises a plurality of frequency resources which are different time resources.
 17. The integrated circuit according to claim 1 wherein the reference signal is a sounding reference signal.
 18. The integrated circuit according to claim 2, wherein the at least one output and the at least one input, in operation, are coupled to an antenna.
 19. An integrated circuit comprising circuitry, which, in operation: maps, in at least one mode of operation, a reference signal to each of one or more frequency resources, into which a frequency band having a transmission bandwidth is uniformly divided depending on a size variation of the transmission bandwidth within a system bandwidth, wherein the transmission bandwidth is provided between control channels mapped to both ends of the system bandwidth; and controls, in at least the one mode of operation, transmission of the reference signal.
 20. The integrated circuit according to claim 19, comprising: at least one input coupled to the circuitry, wherein the at least one input, in operation, inputs data; and at least one output coupled to the circuity, wherein the at least one output, in operation, outputs data.
 21. The integrated circuit according to claim 19 wherein the transmission bandwidth is variable in the system bandwidth while a central frequency of the transmission bandwidth remains the same.
 22. The integrated circuit according to claim 19 wherein in at least one mode of operation, each of the one or more frequency resources has a fixed bandwidth regardless of the variation of the transmission bandwidth.
 23. The integrated circuit according to claim 19 wherein in at least one mode of operation, the one or more frequency resources are uniformly dispersed in the frequency band having the transmission bandwidth.
 24. The integrated circuit according to claim 19, wherein the circuitry, in operation, controls, in at least the one mode of operation, reception of control information associated with a reference-signal mapping, and maps the reference signal based on the control information.
 25. The integrated circuit according to claim 19 wherein the frequency band having the transmission bandwidth is obtained by subtracting a band, to which the control channels are mapped, from the system bandwidth.
 26. The integrated circuit according to claim 19 wherein in at least one mode of operation, each of the one or more frequency resources has a narrow bandwidth, and the transmission bandwidth is a wide bandwidth.
 27. The integrated circuit according to claim 19 wherein in at least one mode of operation, the one or more frequency resources consists of a single frequency resource having the transmission bandwidth.
 28. The integrated circuit according to claim 19 wherein in at least one mode of operation, the one or more frequency resources comprises a plurality of frequency resources and the circuitry maps the reference signal with frequency hopping using each of the plurality of frequency resources.
 29. The integrated circuit according to claim 19 wherein in at least one mode of operation, the one or more frequency resources consists of a single frequency resource having the transmission bandwidth and the circuity maps the reference signal without frequency hopping.
 30. The integrated circuit according to claim 19 wherein the transmission bandwidth is one of a plurality of different transmission bandwidths.
 31. The integrated circuit according to claim 19 wherein each of the one or more frequency resources is a unit of transmission of a reference signal.
 32. The integrated circuit according to claim 19 wherein a number of the one or more frequency resources is different depending on the variation of the transmission bandwidth.
 33. The integrated circuit according to claim 19 wherein the one or more frequency resources cover the frequency band of the transmission bandwidth.
 34. The integrated circuit according to claim 19 wherein in at least one mode of operation, the one or more frequency resources comprises a plurality of frequency resources which are different time resources.
 35. The integrated circuit according to claim 19 wherein the reference signal is a sounding reference signal.
 36. The integrated circuit according to claim 20, wherein the at least one output and the at least one input, in operation, are coupled to an antenna. 